JPH074607B2 - Precision rolling method for bars - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a billet made of steel or non-ferrous metal as a bar material,
The present invention relates to a precision rolling method for rolling a wire rod, a pipe rod, or another long rod having a circular or annular cross section (hereinafter, referred to as a rod or the like).

(B) Conventional technology For example, continuous rolling bloom is usually used in rolling of bar steel. The continuous casting bloom is slab-rolled to a billet at a slab, and after reheating, the billet is rolled into various products at a steel bar factory or a wire rod factory.

Fig. 1 shows a typical layout of a conventional hot rolling line for bars and the like. After the billet is reheated in the furnace 1,
After passing through the group of rough rolling mills 2, the group of intermediate rolling mills 3, and the group of finish rolling mills 4, the product is rolled into a product such as a bar and cooled in the cooling floor 5. For example, a billet having a square cross section of 150 to 180 mm and a length of 12 to 14 m is rolled into a round bar having a diameter of 13 to 100 mm.

The conventional finish rolling mill group 4 is made of a normal two-way roll rolling mill. However, it is expected that the use of a three-way rolling mill will further improve the shape and dimensional accuracy. However, since the effective axial force measuring device and the section profiler have not been developed so far, the excellent function of the three-way rolling mill has not been fully exerted.

Generally, in finish rolling of bar material, in the case of continuous type,
The equipment was arranged such that a loop was formed between the stands to maintain no tension, or the stands were brought close to each other so that the front and rear ends of the rolled material whose axial force changes were made as short as possible. In the latter case, the axial force changes due to external disturbances in addition to the front and rear end portions of the rolled material, resulting in unstable dimensional shape.

A typical example of the three-way rolling mill is shown in FIG. In the three-way rolling mill 40, an upper roll 42 is fixed to an input shaft 41, two lower rolls 43 and 44 are provided at positions intersecting each other at an angle of 120 °, and a rotating force is exerted by each bevel gear 45. Reportedly. The rolled material 11 is rolled by a hole die formed at the central intersection of the three rolls 42, 43, 44. Rolled material 11 is a round bar,
Generally, it is a polygon of a multiple of 3 such as a tube, a hexagonal bar, and a triangular bar.

The characteristic of the three-way rolling mill 40 is that it has better working efficiency and better dimensional accuracy than the two-way rolling mill. When using this with multiple stands continuously, it is usually inverted 180 ° with respect to the horizontal axis passing through the center of the rolled material and the roll arrangement is changed to Y type and λ−
Used in continuous combination of any number of Y-λ-Y.

If the axial force and the cross-sectional profile of the rolled material 11 can be effectively measured in the three-way rolling mill 40, the function of the rolling mill 40 can be sufficiently exerted and the rolling mill group can be effectively utilized.

Therefore, the applicant developed a method for measuring the axial force of a rolled material in a three-way rolling mill and filed a separate application (Japanese Patent Application No. 61-73).
No.787). In this method, as shown in FIGS. 3 and 4, the housing 46 of the three-way rolling mill 40 is slidably installed in a machine frame 47, and the housing is supported by a load meter 48 installed at a predetermined position, and rolling is performed. It measures the axial force of the material.

On the other hand, the three-direction beam projection method in the present invention is an invention method developed by the present applicant and has already been disclosed (Japanese Patent Publication No. 62-39681).

As shown in FIG. 5, this measuring method uses projection beams B ₁ , B ₂ and B ₃ having projection directions and widths along the cross section of the object 11 whose profile is to be measured, as first projection means and second projection means. The projection beam radiating from the means and the third projection means to the area including the outer circumference of the cross section, and the projection beam in contact with the outer circumference of the cross section of the first projection means, the projection beam in contact with the outer circumference of the cross section of the second projection means, and the outer circumference of the cross section of the third projection means. The projection beams in contact with each other are crossed at different intersections, and after the projection beams of the respective projection means have passed through the outer circumference of the cross section, the projection beam detection means D ₁ , D ₂ , D ₃ A tangent line to the portion is detected, and a projection tangent to the cross-sectional outer circumference of the third projection means from the intersection of the projection beam tangential to the cross-sectional outer circumference of the first projection means and the projection beam tangent to the cross-sectional outer circumference of the second projection means. While seeking distance H to the over arm, and the projection means and the cross-section it is relatively rotated, and requests the relationship between the rotation angle θ and the distance H.

In the method of the present invention, it has been confirmed that the cross-sectional profile of a rod or the like can be easily measured by setting the crossing angle of each projection beam to 60 °.

FIG. 6 shows an example of an experimental result in which this profile measuring method is applied to a three-way rolling mill. This experiment was conducted on a round bar having a target dimension of 53.5 mm in diameter. Although the material dimensions before rolling had considerable variation in both major and minor diameters, there was almost no variation in both products after rolling, and the difference between the two was reduced to a maximum of 0.10 mm.

This experiment also demonstrates the superiority of the three-way roll mill.

(C) Problems to be Solved by the Invention Conventionally, in a hot rolling line for bar steel or the like, a two-way roll rolling mill has been used as a finish rolling mill. On the other hand, in recent years, it has been found that the three-way rolling mill has various advantages as compared with the two-way rolling mill, and some of the three-way rolling mills have begun to be used. However, since there is no means for accurately measuring the axial force and cross-sectional profile of the material to be rolled with respect to this three-way roll, the advantages of the three-way roll rolling mill cannot be fully utilized. It was also difficult to control the profile automatically.

(D) Means for Solving the Problems In the method for precision rolling of a bar or the like according to the present invention, at least two stands on the downstream side in a finishing rolling mill group are used in a line for hot rolling from a billet to a bar or the like. Comprising a three-way roll rolling mill, measuring the axial force generated in the rolled material between the three-way rolling mill, measuring the cross-sectional profile of the rolled material by providing a cross-sectional profile meter on the exit side of the finishing rolling mill group By controlling at least one of the reduction amount and the roll rotation speed of the three-way rolling mill based on at least one of the measurement profile and the axial force, the above problems are solved.

In the method of the present invention, one or both of the reduction amount and the roll rotation speed of the three-way rolling mill is controlled based on one or both of the above measurement profile and measurement axial force.

Next, the calculation method of the control signal in the computer will be described.

In FIG. 11, control is started by inputting the product diameter target value D. Furthermore, the tolerances δal ₁ and δal ₂ are input. δal ₁ is the lower limit tolerance, which is usually a positive value of about 0.03 to 0.05 mm. Products with a diameter smaller than the target value will not be manufactured. δal ₂ is the upper limit tolerance, usually 0.10 to 0.15mm
It is a degree.

FIG. 11 shows a control flow. Stages b and c show a control method for setting the diameter X at the portion of the material to be rolled which has passed through the final finishing stand in contact with the roll, to a target value.
Stages d and e show a control method for setting the diameter Y in a portion not in contact with the roll to a target value.

First, the profile is measured using the system of FIG. As a result, as shown in FIG. 14, the roll contact side
The 120 ° intersection angle dimension x = X and the roll non-contact side 120 ° intersection angle dimension y = Y are measured. The division between x and y is determined by the positional relationship of rolls.

In the step b, when X is outside the lower limit tolerance value, that is, is too small, x
Since it must be increased, the operation to increase the finishing stand roll interval is performed. When the manipulated variable is minute, feedback control is performed as it is until it falls within the tolerance.
It is not necessary to reduce g ₁ , g ₂ or the finishing stand rotation speed between b ₂ and b _{3 in} Fig. 11.

This will be described in detail below. As an example, the case where the product diameter is nominally 50 mm is shown below. Normally, δal ₁ = 0.04, δa
l ₂ = 0.12 is adopted. That is, the ultimate goal of control is
D = 50 (nominal diameter) 50 + 0.04 ≦ Y, X ≦ 50 + 0.12 50.04 ≦ Y, X ≦ 50.12.

When X = 50.03 is measured in the b-th stage, there is a slight risk of a negative dimension, that is, a possibility of falling below 50 because it is slightly below the lower limit of tolerance 50.04. Therefore, the control goes to b ₁ so that it becomes about 50.05. b ₁ b ₂ Finishing stand roll spacing Δx
= 0.02mm apart. (Δx has the same meaning as δ.) In this case, the product diameter increased from 50.03 mm to 50.05 mm, but the change in cross-sectional area was The rate of change of cross-sectional area is Assuming that the rotation speed N of the finishing stand drive motor is 1000r.
pm is theoretically In other words, it is necessary to reduce the number of rotations above by 0.8 rpm, but in practice this amount of change falls within the error range, so g ₁ , g as the corrective action between b ₂ and b _{3 2} or finishing stand rpm reduction need not be performed.

When the manipulated variable increases, the rolling condition becomes unbalanced. That is, the roll interval becomes wider, the finish size becomes large, and the mass flow becomes large if the finishing roll rotation speed is constant. However, since the mass flow supplied from the pre-finishing stand is constant, the tensile force between the pre-finishing stand and the finishing stand becomes excessive. As a result, the y dimension changes smaller. Therefore, when this operation amount becomes large, the roll rotation speed of the finishing stand is reduced by ΔN in order to suppress an increase in mass flow calculated by the cross-sectional area change amount ΔA corresponding to this operation amount Δx. As an example, It is the value calculated by.

For more precise control, the control of g ₁ and g _{2 in} FIG. 13 is inserted here instead of reducing the rotational speed by calculation. Originally, the thinning of y is due to the axial force of the material, that is, the tension generated by the imbalance of the rolling conditions. Therefore, the optimum method is to put the tension control here and adjust the rotation speed accordingly.

From the above, depending on the control grade, three methods are selected, namely, reduction of the number of revolutions by calculation between b _{2 and} b _{3 in} FIG. 11, and tension control of g ₁ and g ₂ .

For tension control, as shown in FIG. 13, first, the target tension (F) is input, and the measured value Ft obtained by actually measuring the inter-stand tension is lower than the target tension (F) + allowable tension (δfal). If it is larger, the downstream stand rotation speed is reduced. Ft
Is smaller than (F−δfal), control is performed to increase the downstream stand rotation speed. For this tension control, at least the tension between the final stand (N + 1) and the N stand upstream by one stand may be controlled. If the tension is controlled in the same way among multiple stands, the accuracy will increase.

At the c-th stage, X is outside the upper limit tolerance value, that is, when it is too large, and the reverse operation of the b-th stage is performed. In the d stage, when Y is outside the lower limit tolerance value, that is, when it is too small, it is similar to the b stage, but Y is increased by increasing the supply amount of the material to the finishing stand. Increase the roll spacing of the stand. For d ₂ and d ₃ , operate the pre-finishing stand in the same way as for the b step.

Further, since a slight change in the y dimension can be obtained by a change in tension, the thickness of y may be increased by adding an operation of decreasing the finishing rotation speed to d ₁ and d ₃ . That is, this operation lowers the tension between before and after finishing, so that y increases. This application range is about 0.05mm and the tension setting is 500kg.
This is the case.

At the e stage, Y is outside the upper limit tolerance value, that is, when it is too large, and the reverse operation of the d stage is performed.

The axial force (material tension) control method will be described with reference to FIGS. Usually, the N + 1st stand is the finishing stand.
The tension f = Ft fluctuates depending on the condition fluctuation (material cross-sectional area fluctuation, temperature fluctuation, etc.) on the upstream side of the two sets of the target stands. This typically causes the y dimension to fluctuate, causing Y to be out of tolerance. To prevent this, axial force control is performed. The control contents are as shown in FIG. Quantitatively, the lower limit of axial force detection is actually about 500 kg,
As a guarantee, a 0.1 mm guarantee with 1000 kg detection is practical. This control is a method of controlling the roll rotation speed from the axial force.

As described above, although it is sufficiently practical by itself, if it is incorporated into the overall control that controls the amount of reduction and the roll rotation speed based on the profile and axial force, the most accurate control becomes possible.

As described above, the basis is to measure x and y and control them so as to be in a desired range, that is, D + δal ₁ ≤X≤D + δal ₂ ... D + δal ₁ ≤Y≤D + δal ₂ . Since the fluctuation of y is mostly due to the fluctuation of tension, it may be controlled independently as g ₁ and g ₂ .

(E) Embodiment An embodiment of the method of the present invention will be described with reference to FIG. In the method of the present invention, in a line where hot rolling is continuously performed from a billet to a bar or the like, at least two stands on the downstream side of the rolling mills constituting the finishing rolling mill group 4 are subjected to the three-way roll pressure method. Install the original profiler 6. The measurement result of the cross-sectional profile of the rolled material is sent to the computer 7.

The three-way rolling mill 40 is provided with the axial force detector 8 based on the method for measuring the axial force generated in the rolled material described above. The measurement result of the axial force is sent to the computer 7.

The computer 7 sends a control signal, which will be described later, to the reduction control device 9 and the rotation control device 10 provided in the three-way rolling mill 40 based on these measurement results. The reduction control device 9 and the rotation control device 10 control the reduction amount and the rotation speed of the three-way rolling mill 40 based on the control signal.

Next, the concept of calculating the control signal in the computer 7 will be described.

First, the following simulation is performed based on the experimental result shown in FIG. 6 described above. FIG. 7 shows the case where the target size of the product is 53.5 mm in diameter.

Since the difference between the long diameter and the short diameter is due to the tension acting on the rolled material between the stands, the difference is eliminated by adjusting the motor rotation speed in the direction in which the tension is relaxed. This gives a diameter of 53.40 mm
Align. Next, the target dimension is 53.50 mm, so the reduction device is adjusted. That is, the roll center distance is the radius Only let them separate. This allows Becomes

Since the hole shape of each roll is an arc of 120 °, as shown in FIG. Just go away. At this time, point M is closer to center O It goes away, but points A and B are Only go away from the center O.

Expanding the hole die so that the diameter becomes 53.4 mm to 53.5 mm, the cross-sectional area of the material is Only increase. Therefore, theoretically, the roll speed (motor speed) of this stand should be reduced by 0.4%.

If this roll rotation speed adjustment is not performed at the same time as the roll gap adjustment, the roll is rotating at a speed 0.4% faster than the theoretical rotation speed, tension is again generated between the stands, and the boundary between the rolls ( Usually called an oval.) There is a lack of meat. It is generally estimated that this amount of deficiency is 0.25% in the two-way roll system and 0.05% in the three-way roll system. Therefore, 53.3 mm x 0.05% = 0.027 mm (equivalent to the diameter).

On the other hand, when the conventional type dimension meter is used, the rolling material is sandwiched by the two parallel beams and the distance is instructed. Therefore, the diameter 1 in FIG. 7 is measured. As a result, when adjusting the roll gap by δ = 0.10 mm from 53.4 mm to 53.5 mm, the conventional size gauge Is displayed, and the characteristics of the three-way rolling mill cannot be fully utilized.

Here, the grounds for obtaining the numerical value “0.014” in the above equation will be described. A case of a two-way roll will be described as an example.

When the roll of the finishing stand rotates at the theoretical number of revolutions, the finished product is almost a perfect circle with a diameter of 53.5 mm. But,
In the case of the above example, as a result, the rolls are rotating at a speed 0.4% faster than the theoretical number of revolutions.Therefore, the rolls of the finishing stand are forcibly rolled while pulling the material to be rolled between the pre-finishing stand and the finishing stand. You are doing it. That is, tension is generated between the stands.

In this case, in the two-way roll, as shown in Fig. 15, at the boundary between the upper roll and the lower roll, 53.5 mm × 0.25% = 0.13 mm diameter equivalent 0.13 × 1/2 = 0.065 mm a radius equivalent to a radius oval occurs. Become a state.

As shown in Fig. 16, the three-sided roll has a diaper shape at the boundary of the three rolls, with a thickness of 53.5 mm × 0.05% = 0.027 mm corresponding to a diameter of 0.027 × 1/2 = 0.014 mm.

Here, the values of 0.25% for the two-way roll and 0.05% for the three-way roll are obtained experimentally.

In this way, the numerical value called "0.014" was obtained.

Therefore, in order to eliminate this inconvenience, the profile meter described above was used to measure the movement of each point of the MNL in FIG. 9 to detect δ = 0.10 mm, and the movement of the rolling mill should match the actual dimensions of the rolled material. You can let them do it.

Next, control based on the axial force measurement result will be described.

Conventionally, it is impossible to improve the dimensional accuracy by measuring the axial force of the rolled material and controlling the rotation speed of the drive motor of the roll based on this value to achieve rolling with no tension or constant axial force. , Has already been carried out on two-roll rolling mills of the group of rough rolling mills. However, in the intermediate rolling mill group and the finishing rolling mill group, since the axial force measurement accuracy is actually required to be relatively high, this control has not been achieved. In other words, in the rough rolling mill group, the material cross-sectional area is large, so a value that is practically useful will be relatively rough, but in the intermediate / finishing rolling mill group, the cross-sectional area will be small and useful unless the precision is high. Not a value.

FIG. 10 shows the relationship between the backward tension and the product width dimension in the two-way rolling mill. The symbols in the figure represent the following quantities.

ΔBN: Change in width dimension BN: Width dimension δbN: Stress of material due to tension K: Deformation resistance of material For example, in a rough rolling mill group, when the diameter is equivalent to 100 mm,
Tension 1000 kg, stress 0.13 kg / mm ² , Becomes However, when the deformation resistance K = 25 kg / mm ² , ΔBN =
It is 0.18 mm. That is, the diameter is measured by measuring the tension of 1000 kg.
It can be used to adjust the width dimension of 100 mm to 0.18 mm. However, in the finishing rolling mill group, when the diameter is equivalent to 30 mm, tension 1000 kg, stress 1.17 kg / mm ² , Becomes However, ΔBN = 0.49 mm. When measuring a tension of 1000 kg, only 0.49 mm can be adjusted. Adjustment of 0.1 to 0.2 mm requires 100 kg of tension detection. This is practically difficult.

The value of ΔBN / BN in the three-way rolling mill is about a fraction of that in the three-way rolling mill. Therefore, in the finishing rolling mill group, a diameter of 30 mm, a tension of 1000 kg, a stress of 1.17 kg / mm ² , Becomes However, ΔBN = 0.10 mm. In this case, it is possible to make use of the width dimension of 0.1 mm by measuring the tension of 1000 kg, which is practically sufficient.

As described above, when the three-way rolling mill is used for the finishing rolling mill group, by measuring the axial force of the material, it is possible to make finer adjustments by taking advantage of its characteristics.

(E) Effect According to the method of the present invention, it is possible to fully exhibit the excellent function of the conventional three-way rolling mill, and to manufacture a bar material or the like having a high shape and dimensional accuracy.

[Brief description of drawings]

FIG. 1 is a layout diagram of a hot rolling line for bars and the like to which the method of the present invention is applied. FIG. 2 is a cross-sectional view of a conventional three-way roll rolling mill. FIG. 3 is a drawing similar to FIG. 2 and is a front view of a three-way rolling mill equipped with an axial force measuring device. FIG. 4 is a plan view of FIG. FIG. 5 is an explanatory view of the principle of the conventional profile meter. FIG. 6 is a graph showing the results of rolling by a three-way rolling mill using a conventional profile meter. 7 to 9 are explanatory views of the reduction amount adjustment of the three-way rolling mill. First
Fig. 10 is a graph showing the relationship between the backward tension and the width change of the rolled material by the conventional two-way rolling mill. Fig. 11: Profile measurement, roll reduction (roll spacing or reduction)
It is a flow chart for controlling the increase and decrease of the stand rotation speed, and also shows the case where axial force (tension acting on the material) control is added as g ₁ and g ₂ . Figure 12 is a conceptual diagram when controlling the axial force (tension) in the finishing rolling mill group. FIG. 13 is a flowchart for controlling the roll rotation speed of the stand from the axial force (tension). FIG. 14 is a drawing similar to FIG. 7, and is a supplementary explanatory view of FIG. 7. Explanation of code 2: Rough rolling mill group 3: Intermediate rolling mill group 4: Finishing mill group 6: Profile total 40: Three-way rolling mill

Claims (1)

[Claims] 1. In a line for hot rolling from a billet to a bar or the like, at least two stands on the downstream side in a finishing rolling mill group are constituted by a three-way rolling mill, and rolling materials between the three-way rolling mills. Measuring the axial force generated in, the cross-sectional profile of the rolled material by the exit side three-direction beam projection method of the finishing rolling mill group, the three directions based on at least one of the measurement profile and axial force A precision rolling method for a bar or the like, characterized by controlling at least one of a rolling amount and a roll speed of a roll rolling mill.